Study On Preparation And Adsorption Properties Of Magnetic Particles/Shaped Porous Carbon Pellets Derived From Waste Biomass Of Vallisneria Natans

A large amount of biomass solid wastes are produced every year in China,which bring serious harm to human beings and their survival environment.How to recycle and utilize it as a resource has become a hot issue.Biomass adsorbent was prepared from organic solid waste as raw material,which showed the characteristics such as low cost,high efficiency,renewable and so on.Moreover,it has broad space for development in the field of wastewater treatment applications and waste gas purification technologies.In this paper,in view of the difficulty of separation and recovery of powdered biomass adsorbents and limitation of their application in the field of environmental pollution control,the magnetized and shaping biomass adsorbent materials were prepared from waste Vallisneria natans?V.natans?.The physicochemical properties of the materials,adsorption performance and mechanisms of typical pollutants in water and gas phase on the materials were studied.The main results obtained are as follows:?1?The magnetic particle biosorbent was successfully prepared by chemical precipitation method using waste V.natans as raw materials,FeSO₄·7H₂O and FeCl₃·6H₂O as iron precursor,respectively.The magnetic biosorbent was characterized by a variety of techniques.The adsorption performance and behavior of methylene blue?MB?dye onto magnetic V.natans were investigated,and its magnetic separation ability was also elucidated.The results showed that the Brunauer-Emmett-Teller?BET?specific surface area increased from 3.575 m²/g to 7.434 m²/g.The total pore volume increased from 0.004 cm³/g to 0.013 cm³/g.The results of X-ray diffraction?XRU?and X-ray photoelectron spectroscopy?XPS?indicated that the magnetic ?-Fe₂O₃ crystals were generated,and magnetic V.natans could be separated rapidly under proper magnetic field.The adsorbent dosage had a great influence on the adsorption performance of MB on both non-magnetic and magnetic biosorbent.However,the influence of solution temperature and pH was insignificant.Adsorption kinetics and isothermal studies showed that the adsorption behavior of MB on the two adsorbents was consistent with the pseudo-second-order kinetic model and Dubinin-Radushkevich?D-R?isothermal adsorption model,respectively.Moreover,thermodynamic studies showed that the adsorption process of MB on two adsorbents was spontaneous and exothermic.According to the Langmuir isothermal model,the monolayer adsorption capacities of MB on the non-magnetic and magnetic V.natans were 657.90 mg/g and 473.93 mg/g at 303 K,respectively.?2?The light carbon pellets?BCPs-ZnCl₂?was successfully prepared from waste V.natans by combining the liquefaction,resinification,hydrothermal and thermal activation technology with ZnCl₂ as chemical activator.The surface morphology,material composition,specific surface area and pore structure of BCPs-ZnCl₂ were characterized by scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FT-IR?,nitrogen adsorption-desorption and so on.Based on the adsorption efficiency of metronidazole?MNZ?on BCPs-ZnCl₂,the optimum preparation conditions were obtained:the mass ratio of dried powder of V.natans and ZnCl₂ 1:2.4,the carbonization temperature 600? and carbonization time 90 min,respectively.BCPs-ZnCl₂ showed low volume density and high mechanical strength,with an average particle size of 5 mm.Its BET specific surface area,total pore volume?V,?and micropore volume?Vmic?were 922.56 m²/g,0.421 cm³/g and 0.386 cm³/g,respectively.?3?The adsorption performance and behavior of typical antibiotic drugs such as metronidazole and dimetridazole?DMZ?in aqueous phase on BCPs-ZnCl₂ were studied.The optimum adsorption conditions were the adsorbent dosage of 5 g/L,natural pH and temperature of 30 ?,and the removal efficiencies of MNZ and DMZ reached 96.7%and 97.0%,respectively.The adsorption process of MNZ and DMZ on BCPs-ZnCl₂ fitted pseudo-first-order kinetics model well.The isothermal adsorption studies showed that the adsorption of MNZ and DMZ followed to the Langmuir adsorption model and D-R model,respectively.The maximum monolayer adsorption capacities were 64.23 mg/g and 82.58 mg/g for MNZ and DMZ,respectively.Moreover,the adsorption process of MNZ and DMZ on BCPs-ZnCl₂ was spontaneous and endothermic.The adsorption mechanisms mainly included hydrogen bond,?-?electron dispersion and micropore filling.?4?Using BCPs-ZnCl₂ as adsorbent and xylene as typical representative of volatile organic pollutants?VOCs?,the adsorption performance and behavior of xylene on BCPs-ZnCl₂ were studied by headspace gas chromatography.The optimum adsorption conditions were 0.1 g of adsorbent dosage,40 ? of system temperature and 30%relative humidity.When the initial concentration of xylene was 3.464 g/m3,the removal efficiency reached 100%after 90 min adsorption.The adsorption kinetics data showed that the adsorption process of xylene was consistent with the pseudo-second-order kinetic model,and the isothermal adsorption process fitted the Langmuir model well,the maximum monolayer adsorption capacity was 250.63 mg/g.Thermodynamic studies showed that the adsorption of xylene on BCPs-ZnCl₂ was a spontaneous and endothermic process.Micropore filling and ?-? electron dispersion interaction were dominant.